Re: [PATCH] mount.cifs: don't send a mandatory ver= option to the kernel

[Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>]

On Thu, 17 May 2012 12:58:45 -0500
Steve French <smfrench-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> On Thu, May 17, 2012 at 12:54 PM, Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org> wrote:
> > On Thu, 17 May 2012 12:03:26 -0500
> > Steve French <smfrench-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >
> >> On Thu, May 17, 2012 at 11:44 AM, Sachin Prabhu <sprabhu-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> >> > On Fri, 2012-05-11 at 15:03 -0400, Jeff Layton wrote:
> >> >> Traditionally, this ver= option was used to specify the "options
> >> >> version" that we're passing in. It has always been set to '1' though
> >> >> and we have never changed that.
> >> >>
> >> >> Eventually we want to have a ver= (or vers=) option that allows users
> >> >> to specify the SMB version that they want to use to talk to the server.
> >> >>
> >> >> At that point, this option will just get in the way. Let's go ahead
> >> >> and remove it now in preparation for that day.
> >> >>
> >> >
> >> > Do we need 'ver=' mount option to specify the SMB version number? Isn't
> >> > 'vers=' sufficient for this?
> >>
> >> Yes - "vers" is sufficient (although I am fine with adding synonyms to
> >> make it easier for nfs users - e.g. "smbvers=" or if we want to have
> >> smb2 specific utility programs (e.g. for a phone or tablet) that call
> >> do_mount automatically set vers=2.1.
> ...
> > Yes, I don't think we're going to use ver= as a synonym for vers=.
> >
> > That said, we haven't needed a way for the kernel to recognize the
> > userspace "options version" and no other userspace mount helper that
> > I'm aware of has such a thing. After all, a userspace mount helper
> > isn't even required...someone can mount cifs just fine w/o one as long
> > as they pass in ip=.
> >
> > Handling an options version is more of a problem with binary mount
> > options, where you need to know if you're breaking the ABI. With text
> > based options, it's just not an issue.
> >
> > So I think going ahead and getting rid of this in the kernel is the
> > right thing to do. It's just useless cruft that may get in the way in
> > the future.
> >
> > If the kernel ever needs to determine the mount helper "version" for
> > some reason, then it can treat a lack of ver= at all identically to how
> > it handles a helper that passes in ver=1.
> 
> The main case I can think of is debugging - there were a few times
> that I have wanted to know the mount.cifs version in looking at dmesg
> output of mount failures.   On a normal linux distro you can go to the
> package manager or simply go to bash and type mount.cifs -V that isn't
> as practical on a phone or on some Linux tablets.
> 


If that's the case, then what we have now is completely inadequate to
that task, since the mount helper has always passed in "ver=1". That
doesn't tell you anything about the actual version in use.

-- 
Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>